High-performance energy transfer method for thermal processing applications

ABSTRACT

An apparatus and method supports thermal processing of a microelectronic device such as a semiconductor chip in a substrate by heating the substrate with secondary radiation from an energy transfer device  40 , which has a first set of energy transfer regions comprised of an emissive and thermally conductive material, and a second set of thermally insulating regions comprised of a reduced emissivity and reduced thermal conductivity material or free space. A multi-zone-radiant energy source  30  provides radiative energy to energy transfer device  40 , with a process controller  36 , preferably a multi-zone controller, altering the amount of energy provided by each heat zone associated with each emissive region of energy transfer device  40 . Sensors detect the thermal energy level of each energy transfer region to allow controller  36  to adjust the secondary radiation emitted by each region in real time, resulting in a predetermined and controlled distribution of thermal energy on substrate  20 . Energy transfer device  40  can have plural emissive and thermally conductive concentric rings separated from each other by reduced emissivity and reduced thermal conductivity regions such as free space gaps  42 . Alternatively, a solid plate  54  having an emissive coating or emissive surface  52  can have reduced emissivity and reduced conductivity isolation regions such as trenches  56  for defining the multi-zone high-emissivity and high thermal conductivity energy transfer regions.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional from U.S. patent application Ser. No.09/067,142, filed Apr. 27, 1998 now U.S. Pat. No. 6,188,044, Feb. 13,2001 and entitle “HIGH-PERFORMANCE ENERGY TRANSFER SYSTEM AND METHOD FORTHERMAL PROCESSING APPLICATION”.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a method and system for devicefabrication on a substrate and, more particularly, to a method andsystem for transferring energy from a radiative energy source to asubstrate for rapid thermal processing applications in support ofmicroelectronic and semiconductor device fabrication.

BACKGROUND OF THE INVENTION

Semiconductor devices can be formed on silicon wafer substrates by theuse of certain fabrication processes some of which involve theapplication of heat (e.g., in the range of 200° C. to 1100° C.) to thesubstrate in a controlled environment. Several processing methods forfabricating a device onto a substrate have evolved which include theapplication of thermal energy to the substrate to drive thermallyactivated fabrication processes. For instance, chemical-vapor deposition(CVD) processes can deposit various materials on a substrate, includingmetallic, semiconductor and insulating material layers. Thermaldeposition processes and thermal anneal processes can support silicideformation. These chemical and thermal processes can form amicroelectronic device such as an insulated gate field-effect transistor(IGFET) on a substrate by manipulating, forming or modifying materialssuch as silicon dioxide, silicon nitride, tungsten, polysilicon andother known materials. Well-known single-wafer rapid thermal processing(RTP) applications include rapid thermal annealing (RTA), rapid thermaloxidation (RTO), rapid thermal chemical-vapor deposition (RTCVD)processes, and rapid thermal nitridation (RTN).

During the formation of a device such as an IGFET on a substrate bythermal processing techniques such as RTP methods, consistent productionof a high-quality semiconductor integrated circuit (IC) with highproduction yield is enabled when the thermal energy is applied in auniform and repeatable manner. CVC, Inc. (“CVC”) has introduced severalsignificant improvements over conventional thermal processing systemsand methods for semiconductor IC fabrication. For instance, CVC hasdeveloped a multi-zone radiant-energy illuminator for producing heat insilicon substrates during device fabrication as is disclosed in U.S.patent application Ser. No. 08/678,321 filed on Jul. 11, 1996, andentitled “Multi-Zone Illuminator for Rapid Thermal Processing,” which isincorporated herein by reference as if fully set forth. This multi-zoneilluminator provides improved wafer-to-wafer process and temperaturerepeatability as well as within-wafer temperature uniformity bymonitoring and controlling optical energy produced by plural lampsarranged in multiple heating zones. The multi-zone illuminator alsoincludes a multi-zone temperature measurement system having pluralpyrometry sensors for real-time wafer temperature measurement.

Although the multi-zone illuminator provides improved device fabricationuniformity and repeatability, a number of process control difficultiesremain with respect to fabrication by rapid thermal processing (RTP).For instance, in one implementation of rapid thermal processing (“RTP”)or rapid thermal chemical-vapor deposition (“RTCVD”), a substrate isgenerally supported by a susceptor during the application of heat. Thesusceptor can absorb the radiant optical energy and redistribute thermalenergy across the substrate thus nullifying or minimizing effectivenessof the control inputs to a multi-zone illuminator. Another limitationrelates to the varying emissivity of the substrate during processing dueto the dependence of substrate emissivity on temperature and thin films.Although CVC's multi-zone temperature sensing and control technology inconjunction with multi-zone illuminators can compensate for variationsin wafer emissivity (due to any source such as temperature and/ormaterial layers), this compensation can introduce some errors andrequires complicated control algorithms which can depend upon extensivetesting and calibration runs for each type of substrate being processed.Another difficulty relates to the size and makeup of the susceptor usedto support a substrate. The heating susceptor can introduce residuecontaminants (e.g., metallic contaminants) to the substrate when thesusceptor is in physical contact with the substrate. Also, to provideadequate mechanical support of the substrate, the susceptor can be madeof a relatively large mass of thermally conductive material. The largerthe mass of a conventional heating susceptor, the more difficult it isto estimate and control the heat energy absorbed and emitted by thesusceptor. Moreover, high-thermal-mass susceptors significantly slowdown the wafer heating and cooling times, resulting in reduced waferprocessing throughout.

SUMMARY OF THE INVENTION

Therefore a need has arisen for a method and apparatus that providesimproved temperature control and uniformity during thermal processing ofa substrate during fabrication of semiconductor devices on the substratein a thermal processing equipment.

A further need exists for a method and apparatus that provides improvedaccuracy and repeatability in measuring the temperature distribution ofa substrate during thermal processing applications.

A further need exists for a method and apparatus that provides enhancedspatial control of incident optical radiation to improve the accuracy,uniformity, and repeatability with which a multi-zone illuminator heatsa substrate in rapid thermal processing (RTP) including rapid thermalchemical-vapor deposition (RTCVD) applications.

In accordance with the present invention, a high-performance radiantenergy transfer system and method is provided that substantiallyeliminates or reduces disadvantages and problems associated withpreviously developed methods and apparatus for providing energy to asubstrate during thermal processing (e.g., in RTP and RTCVD) for thefabrication of a device such as semiconductor chips. A housing-forming areactor process chamber can be used to isolate a substrate for thermalprocessing (such as RTA, RTO, RTN, or RTCVD). A radiative heat sourcesuch as a multi-zone illuminator can direct radiative energy flux at thesubstrate to provide thermal energy in support of the thermalfabrication process. An energy transfer device can be disposed betweenthe substrate and the heat source to efficiently and accurately andrepeatably transfer energy originated from the radiative energy sourceto the substrate. The energy transfer device can also substantiallydecouple the substrate heating as well as temperature measurement andcontrol tasks from the substrate emissivity effects. The energy transferdevice can comprise first and second regions, the first regions having afirst emissivity and thermal conductivity, and the second regions havinga second emissivity and thermal conductivity wherein the first regionscan provide a higher degree of energy transfer and the second regionscan provide a lower degree of energy transfer. The low energy transfercharacteristics of the second regions allow the second regions to act asspacers or energy zone buffers that separate the first regions from eachother. In one embodiment, the second regions can be empty spaces formedbetween adjacent first regions. This arrangement enables excellentmulti-zone substrate heating and temperature control via improvedcontrollability of the spatial profile of the incident radiant power onthe substrate.

More specifically, the reactor chamber can support any conventionalthermal processing system or method for device fabrication onto asubstrate, including single-wafer RTP and RTCVD. The radiative energysource can include any known equipment for thermal processing, includingthe multi-zone illuminator available through CVC, Inc. The radiativeenergy source can provide thermal energy with conventional tungstenhalogen lamps arranged in plural spatially resolved heating zones, suchas the concentric or spiral lamp distribution arrangements developed byCVC. The radiant energy provided by the multi-zone illuminator, can becontrolled by a multi-zone controller and related temperature sensorsassociated with each zone and can be adjusted in real time on azone-by-zone basis by the multi-zone controller associated with theilluminator power supplies and the temperature sensors.

The energy transfer device can include plural energy transfer regions orzones having the first emissivity and/or thermal conductivity, theenergy transfer regions disposed so that each first region is associated(in terms of radiant energy transfer) with one or more zones in themulti-zone illuminator. The energy transfer regions can have a highemissivity, meaning that each energy transfer region can absorb (fromthe illuminator) and emit (mostly to the substrate) all or nearly all ofthe energy directed at it; and/or, the energy transfer regions can havea relatively high thermal conductivity, meaning that each region candiffuse or distribute thermal energy freely within itself. The energytransfer regions can be separated from each other with plural thermallyinsulating regions having the second reduced emissivity and/or reducedthermal conductivity.

The thermally insulating regions can have a low emissivity, meaning thatthey absorb and emit very little or a small fraction of the energydirected at them; and/or the insulating regions can have a low thermalconductivity, meaning that each insulating region resists the diffusionof heat within itself and between neighboring high-emissivity regions.Thus, the thermally insulating regions can divide up the energy transferregions so that substantially all or most of the radiant energyassociated with each zone of the multi-zone illuminator is translated tothat zone's associated energy transfer region (or regions), and so thatthe energy transfer regions transfer very little thermal energy betweeneach other in the form of heat conduction due to the low thermalconductivity of the thermally insulating regions. In addition, thethermally insulating regions can have special geometric designs toreduce energy absorption, such as a significantly smaller exposedsurface area compared to the energy transfer regions (such as smallfree-space gaps between the high-emissivity regions).

The energy transfer device can comprise a central disk and pluralconcentric rings disposed about the central disk, the central disk andthe concentric rings forming higher-emissivity energy transfer regions.An insulating region can be inserted at the inner circumference of eachconcentric ring. In one embodiment, the energy transfer regions ofconcentric rings are comprised of silicon carbide (or aluminum nitride,or graphite, or boron nitride or silicon) and the insulating regions arecomprised of free-space gaps. In another embodiment, the energy transferdevice can be formed from a single contiguous plate having insulating sregions etched into or embedded in the plate between each alternatingenergy transfer region (or within the high-emissivity region).

The energy transfer device of the present invention can support thermalprocessing of various substrates such as silicon through secondaryradiation. A radiative energy source having plural radiant energy zonescan be directed at the energy transfer device with one or more specificradiant energy zones operable to provide a predetermined and controlledamount of radiative energy (adjustable and controllable in real time).An emissive region can be associated with at least one of each suchradiant energy zones to absorb most or substantially all of theradiative energy projected onto the surface of the energy transferregion and to provide secondary radiative energy to the substrate. Atemperature sensor can measure the temperature of each emissive regionto determine the amount of secondary radiative energy being transferredto the substrate and to extract the projected substrate temperature. Amulti-zone controller associated with the radiative energy source canadjust the energy level of each emissive region in real-time by alteringthe amount of radiative energy provided by the one or more radiant zonesassociated with each region.

The high performance energy transfer system and method according to thepresent invention provides important technical advantages. The energytransfer device maps one or more specific zones of a multi-zonecontrolled radiative energy source to a particular zone on the heatedsubstrate within a processing chamber, thus providing the multi-zonecontrol authority needed for real-time temperature uniformity controland for excellent repeatability of thermal fabrication processes.

Another important technical advantage is that the energy transfer devicecan be constructed with materials having characteristics which allowaccurate and repeatable measurement of each region's energy level ortemperature. Thus, the output signals of the real-time sensors can beused by a multi-zone controller to accurately adjust the energy providedto each region by specific sets of associated zones without anysignificant interference effects or errors caused by wafer emissivityvariations.

Another important technical advantage of the present invention is thatthe energy transfer device can be placed proximate to but not in contactwith the substrate, thus avoiding contamination of the substrate by theenergy transfer device. The distance between the substrate and theenergy transfer device can advantageously be adjusted to accuratelycontrol the secondary radiation pattern projected by the energy transferdevice to the substrate (and also the degree of separations of energyprofiles from different zones). For instance, the distance between thesubstrate and the energy transfer device can be arranged so as to beless than the width of the radiation rings (e.g., for a radiation ringwidth of 5 mm, the distance between the substrate and the energytransfer device is chosen to be preferably in the range of ˜1 mm to ˜5mm).

Another important technical advantage is that, in a configuration inwhich the energy transfer device does not directly support thesubstrate, the energy transfer device can be constructed of a relativelysmall mass of a material, resulting in small thermal mass and rapidthermal response. The smaller is the mass of the energy transfer devicefor a given type of material, the quicker is the response of the energytransfer device to increased energy input, or the removal of energy dueto reduced input radiant energy, thus providing faster heating andcooling rates than conventional contact susceptors can provide.

Another important technical advantage is achieved by the partitioningand separation of the energy transfer device into separate zones. Theseseparations preferably have circular symmetry for processing of circularwafers. The average radial dimensions or widths of the segmented piecesare significantly smaller than the radial dimension of a solid platepiece, which allows the use of individually controllablelow-thermal-mass parts. Thus, the radial temperature distributionprofile of a given radiation transfer ring will be established in a muchfaster time frame compared with a conventional large-area plate piece ofthe same thickness. The thickness of the radiation transfer ring, andtherefor its thermal mass, can be made much smaller, making thisinvention suitable for all RTP (e.g., RTA, RTO, RTN, RTCVD, etc.)application.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention and advantagesthereof may be acquired by referring to the following description takenin conjunction with the accompanying drawings in which like referencenumbers indicate like features and wherein:

FIG. 1 depicts a side cutaway view of a single-wafer thermal processingsystem such as a multi-zone RTP system according to the presentinvention;

FIG. 2 depicts a top view of one preferred embodiment of an energytransfer device;

FIG. 2a depicts a top view of a multi-zone illuminator;

FIG. 3 depicts a side cutaway view of another embodiment of an energytransfer device constructed from a solid plate;

FIG. 4 depicts a spider leg support for an energy transfer device;

FIG. 5 depicts a substrate and energy transfer rings supported andadjusted by pins;

FIG. 6 depicts one embodiment of an energy transfer device formed withplural gaps cut into a single plate; and

FIG. 7 depicts an alternative embodiment of the thermal processingsystem configured with the energy transfer device directed at the backside of the substrate.

DETAILED DESCRIPTION OF THE INVENTION

Preferred embodiments of the present invention are illustrated in theFIGURES, like numerals being used to refer to like and correspondingparts of the various drawings.

The use of an energy transfer device improves controllability andrepeatability for microelectronic device fabrication onto a substrate(such as fabrication of semiconductor silicon chips) by the use of anyof a number of conventional thermal processing systems and methods.Conventional thermal processing systems and methods such as RTP systemshave difficulty achieving high controllability and repeatability fordevice fabrication due to the inability to independently control thetemperature profile within a substrate in real time. Conventionalsystems attempt to achieve uniform and repeatable temperature patternsfor each substrate processed by measuring the energy level of thesubstrate on a single point throughout the thermal process. However,accurate temperature measurement and control are difficult to achievefor different zones or regions within the substrate. The energy transferdevice of this invention improves upon conventional heating susceptorsby allowing separation of zones and therefor providing enhancedmulti-zone control capability and also by reducing the chance ofsubstrate contamination through noncontact operation.

In addition, the use of an energy transfer device having a controlledand highly emissive surface allows accurate temperature measurement andcontrol substantially independent of substrate emissivity effects.Pyrometry methods can measure substrate energy levels but pyrometrymeasurements depend upon consistent and fixed emissivity characteristicsof the substrate through the heating process. When substrate emissivitycharacteristics vary, as frequently occurs during substrate heating (dueto temperature effects, depositions of material layers, and/orvariations of starting substrate materials), accurate temperaturemeasurement and control cannot be accomplished without compensating forthese variations. The use of an energy transfer device used as a bufferbetween the substrate and the radiant source improves upon direct waferheating and temperature measurement by allowing emissivity independentsubstrate temperature measurement and control.

To increase the accuracy and repeatability of energy levels applied tosubstrates during thermal processing, the present invention appliesenergy to the substrate by using secondary radiation emitted from anenergy transfer device. Referring now to FIG. 1, a side cutaway view ofa thermal processing system such as an RTP system for device fabricationonto a substrate is depicted. The thermal processing system 10 depictedby FIG. 1 is a simplified depiction of a system adapted foraccomplishing multi-zone rapid thermal processing (RTP). It should beunderstood that the present invention can be adapted to support otherthermal processing apparatus and methods for the fabrication ofmicroelectronic devices onto a substrate such as a semiconductor wafer.

A housing 12 defines a reactor process chamber 14 which can isolate asubstrate in a controlled environment during thermal processing. Avacuum pump port 16 associated with housing 12 can be used to evacuateor otherwise control the pressure of process chamber 14 in conjunctionwith low-pressure RTP (e.g., RTCVD) processes. A gas injector showerhead18 (preferably with a highly optically reflective surface) can providereactive gases for supporting device fabrication in reactor chamber 14.A substrate 20 is disposed in reactor chamber 14 so that its frontsideor active device side 22 is exposed to reactive gases provided toreactor chamber 14 by gas injection showerhead 18 (preferably with ahighly optically reflective surface). Substrate backside 24 can beisolated from the reactive gases by a substrate support structure 26 inconjunction with a backside purge mechanism. Housing 12 and substratesupport structure 26 can be comprised of conventional materials, such asstainless steel (for the process chamber) and quartz (for substratesupport). A wafer transfer port 28 associated with housing 12 can allowloading and unloading of substrate 20 into and out of reactor chamber 14by conventional techniques such as a central wafer handling system.

A multi-zone radiative energy source 30 provides radiant optical energytowards energy transfer device 40, energy transfer device 40 in turnre-radiating energy toward the backside 24 of substrate 20. Multi-zoneradiative energy source 30 is preferably a multi-zone illuminator withplural lamp zones 32 for providing radiative optical energy, and pluralembedded pyrometry sensors 34 for detecting radiation (and correspondingtemperature values) at varying radial positions. The lamps are groupedor partitioned into multiple heat zones as described herein. Amulti-zone controller 36 interfaces with power supplies 31 for radiativeenergy source 30 and pyrometry sensors 34 to adjust the optical fluxvalues emitted by the lamps 32 in the zones according to the energylevels or corresponding temperatures detected by the pyrometry sensors34. A quartz window 38 separates multi-zone radiative energy source 30from substrate 20 without significantly decreasing the transfer ofenergy from lamps 32 to the backside of energy transfer device 40.

Energy transfer device 40 is disposed between multi-zone radiativeenergy source 30 and substrate 20. Energy transfer device 40 has acentral disk region D, a first concentric ring region R1, and a secondconcentric ring region R2 (multiple additional rings may be used ifnecessary). Each region of energy transfer device 40 is associated withat least one or more zones of multi-zone radiative energy source 30, asis depicted by dotted lines 41, which show that each region is generallyassociated with a set of lamps 32 located in each zone of multi-zoneradiative energy source 30 as well as a temperature sensor. Between eachpair of regions is a free space gap 42 which separates the regions fromeach other. Free space gap 42 inhibits or suppress the direct transferof thermal energy between adjacent regions. Thus, energy emitted fromlamps 32 in zones associated with a region can be absorbed by the regionwithout significant transfer or redistribution of energy occurringbetween the associated region and adjacent regions.

The relationship between energy transfer device 40 and multi-zoneradiative energy source 30 can be better understood by reference to FIG.2, which depicts a top view of energy transfer device 40, and FIG. 2a,which depicts a top view of multi-zone radiative energy source 30.Energy transfer device 40 shown in FIG. 2 has three energy transferregions having high thermal conductivity and high emissivity properties:a centrally located circular shaped disk D, a first concentric ring R1and a second concentric ring R2 (more number of rings may be used). Thethree emissive regions are separated from each other by two insulatingregions, the insulating regions having reduced thermal conductivity andreduced emissivity properties. A first free space gap 42 exists betweenthe inner circumference of concentric ring R1 and the outercircumference of central disk D. A second free space gap 42 existsbetween the outer circumference of concentric ring R1 and the innercircumference of the concentric ring R2. Central disk D and concentricrings R1 and R2 are comprised of a radiation-absorptive andthermally-conductive material which can absorb radiant optical energyand laterally diffuse radiative heat and emit secondary radiation toprovide selective spatially resolved heating of different radialpositions along backside 24 of substrate 20. Predetermined radialpositions along substrate 20 can be selectively heated by adjusting theamounts of radiative energy absorbed and re-emitted from each emissiveregion of energy transfer device 40 that is associated with thepredetermined radial position.

Referring to FIG. 2a, multi-zone radiative energy source 30 has plurallamps 32 disposed in plural heating zones so that, in one particularconfiguration, each heating zone can correspond to at least one emissiveregion (or plural emissive region) of energy transfer device 40. Forinstance, Zone Z_(D) can associate with region D, zone Z₁ can associatewith region R1, and zone Z₂ can associate with region R2. Eachcircularly symmetric heating zone can be aligned with energy transferdevice 40 to direct substantially all of the radiative energy producedby each zone to selectively heat its associated high thermalconductivity and high emissivity region of energy transfer device 40.Thus, for example, if a central area of substrate 20 needed to be heatedup preferentially over the rest of substrate 20, zone Z_(D) can providegreater energy to region D, which in turn heats up the central region ofsubstrate 20 more than other regions. One or more radiative heat zones,however, can correspond to one or more energy transfer rings. Althoughthe concentric rings of the present embodiment of energy transfer device40 are easily applicable to the circular heating zones of existingradiative energy sources such as multi-zone illuminators, in alternativeembodiments, other non-oxisymmetrical shapes can be used to form theheating zones and energy transfer regions.

Multi-zone radiative energy source 30, energy transfer device 40, andsubstrate 20 are accurately aligned and separated from each other tomaximize the accuracy, repeatability and control of heating applied tosubstrate 20. For instance, the separation between energy transferdevice 40 and substrate 20 can be a distance significantly smaller thanthe width of each concentric ring to help ensure that there is a smallamount of zone-to-zone radiation overlap on the substrate (e.g., for theradiant fluxes incident on the substrate from two adjacent emissiveregions of heat transfer device 40). This ensures the ability forindependent heating of the radial zones in the substrate with excellentspatial resolution. Free space gaps 42 are made large enough to ensurethat direct conductive heat transfer between adjacent concentric ringsis rather negligible, but small enough so that the majority of theradiation from the primary energy source 30 is absorbed by energytransfer device 40 and that majority of substrate heating occurs due tothe radiant energy from heat transfer device 40. In embodiments in whichthe gaps are free spaces, small gaps ensure that direct radiation frommulti-zone radiative energy source 30 to substrate 20 is only a smallfraction of the total energy. The distance between multi-zone radiativeenergy source 30 and energy transfer device 40 is set so thatsubstantially all radiative energy from a heat zone is directed towardsits associated region of energy transfer device 40. In addition, therelationship between the width of each region of energy transfer device40 and the distance between energy transfer device 40 and multi-zoneradiative heat source 30 are set so that each pyrometry sensor 34 canseparately measure the energy level and corresponding temperature of theregion with which it is associated. Alternatively, imaging optics can beused for each pyrometry sensor to limit its view factor to within thewidth of its associated region of energy transfer device 40 so that thedistance between the pyrometric sensor and the radiation transfer device40 can be altered without affecting the pyrometric measurement and eachpyrometry sensor 34 can provide an accurate energy level (andcorresponding temperature) reading of its associated region tomulti-zone controller 36. Controller 36 can then adjust the secondaryradiation directed at substrate 20 by adjusting the primary radiationdirected at energy transfer device 40.

In operation, multi-zone controller 36 adjusts the power to lamps 32which irradiate energy transfer device 40. Energy transfer device 40absorbs incident radiation from lamps 34 and provides secondaryradiation to substrate 20. Pyrometry sensors 34 measure the energy leveland corresponding temperature of each energy transfer region of energytransfer device 40 and provide the energy levels to controller 36.Controller 36 can then accurately estimate the heating that needs to beapplied to substrate 20 and can adjust the power provided to each groupof lamps 32 in zones to adjust the secondary radiation provided by eachemissive region of energy transfer device 40 so that substrate 20 isheated according to a predetermined heating profile. To further improvethe dispersal of heat to substrate 20, rotation mechanism 44 can rotatesubstrate 20 relative to primary multi-zone radiant energy source 30 andrelative to energy transfer device 40 (if desired, energy transferdevice 40 can also rotate with substrate 20). Rotation of substrate 20can average out azimuthal non-uniformities created by geometrical andmaterial deviations over each region within energy transfer device. 40as well as any intra-zone non-uniformities associated with primaryradiant source 30. For instance, rotation of the substrate at a ratefaster than the thermal time constant for lateral thermal diffusion oversubstrate 20 can minimize azimuthal nonuniform effects, particularlywhen the distance between substrate 20 and energy transfer device 40 (orthe material properties of energy transfer device) can vary azimuthally.

In one alternative embodiment, a highly reflective surface (e.g., as anintegral part of showerhead injector plate 46) can be aligned with thefrontside 22 of substrate 20 to reflect substantially all of theradiative energy emitted from substrate frontside 22 back towardssubstrate 20. The reflective surface can be incorporated with a gasinjector as is depicted by reflective gas injector 46 of FIG. 1.

The objective of having a reflective surface opposed to the frontside ofsubstrate 20 is to create an optical cavity system that drives theeffective substrate frontside emissivity towards a value of one. Theeffective emissivity of the substrate frontside in this optical systemis defined by the equation:$E_{effective} = \frac{E_{substrate}}{1 - {R_{showerhead}\left( {1 - E_{substrate}} \right)}}$

where R_(showerhead) is equal to the reflectively of the reflective gasinjector 46. When the showerhead has a reflectivity of one and thelateral dimensions of the wafer, the showerhead and the energy transferdevice are larger than the separation between them, the effectiveemissivity of the substrate frontside within the optical systemapproaches a value of one.

Reflective gas injector 46 minimizes the effects of the emissivity ofsubstrate 20 on the thermal response of substrate 20 to the secondaryradiation emitted by energy transfer device 40. The combination ofhighly emissive regions of energy transfer device 40 and a highlyreflective gas injector 46 provide an optical cavity system thatoptimizes repeatable substrate heating and precision temperaturemeasurement independent of the variable emissivity characteristics ofsubstrate 20.

In alternative embodiments, energy transfer device 40 can be constructedof any material or materials having highly emissive regions separatedfrom each other by substantially non-conductive regions. As used herein,emissive means a region that absorbs and re-emits substantially allradiative energy directed at it, and non-conductive means a region thatallows limited or negligible transfer of thermal energy. The alternatingrings of high and low emissivity regions and high and low thermalconductivity regions depicted in FIG. 2 could be arranged in alternativeconfigurations as needed to associate high emissivity regions with atleast one controllable heat zone so that energy irradiated from the heatzone can be translated by the high emissivity region to a predeterminedregion of a substrate. Further, the energy level of each high emissivityand high thermal conductivity region can be measured by alternativetemperature sensors, including sensors actually physically coupled toeach emissive region. The energy level of each high emissivity regioncan then be adjusted by altering the amount of radiative energy providedby the primary heating zone or zones associated with the high emissivityregion, thus allowing a predictable and controlled amount of secondaryradiation to heat the substrate.

Referring now to FIG. 3, one embodiment of energy transfer device 40 isdepicted. A coating of high emissivity material, such as silicon carbidelatex 52, fares the substrate 20 on one side of energy transfer device40 and fares towards quartz window 38 on the opposite side of energytransfer device 40. Silicon carbide latex 52 is deposited on a plate 54formed of an efficient energy transferring material such as aluminumnitride or boron nitride ceramic materials or graphite. Trenches 56 areformed or machined into plate 54 to define and separate emissive regionsD, R1, and R2. The silicon carbide latex 52 is a highly emissivematerial having an emissivity value approaching 1, whereas the aluminumnitride material exposed in each trench 56 has a reduced emissivity.Additionally, the trenches 56 significantly reduce the thermalconduction between adjacent high emissivity regions. Eachhigh-emissivity region has a contact temperature sensor 60 (or anoncontact pyrometry sensor), such as a thermalcouple, in directphysical contact to allow precise temperature measurements of eachregion. A support pin 58 supports substrate 20 to prevent directphysical contact with energy transfer device 40, and to provide aspacing between the substrate 20 and energy transfer device 40.

The construction of energy transfer device 40 from a single plate ofmaterial can provide a robust system which can endure many thermalcycling stresses without substantially altering its physical properties.Alternatively, an energy transfer device 40 constructed from sets ofseparate pieces can advantageously reduce impact of thermal stresscaused by expansion and contraction of the material. In either case,construction with material having similar thermal expansion coefficientscan be used for enhanced reliability in thermal environments. Forinstance, silicon carbide and aluminum nitride are relatively thermallymatched materials that expand and contract by comparable dimensions whensubjected to thermal energy. Although FIG. 3 depicts substrate 20 asheld proximate to but not touching energy transfer device 40, the solidplate configuration can also physically support substrate 20. However,embodiments in which energy transfer device 40 does not directly supportsubstrate 20 can advantageously be constructed with minimal physicalmass, allowing quicker, more accurate, and more repeatable heatingresponses.

Referring now to FIG. 4, a spider leg support 48 is depicted which canprovide physical support to energy transfer device 40, whether formed asseparate concentric rings or as a single plate. Spider leg support 48provides one implementation where supports for energy transfer regionsare placed directly onto a transparent substructure such as the quartzwindow in an RTP system. Plural supports 50 in resting engagement witheach region of energy transfer device 40 can hold each region in apredetermined position relative to substrate 20. Spider leg support 48can be incorporated with quartz window 38, and can be used whensubstrate 20 is rotated with substrate support 26 relative to energytransfer device 40 (and relative to multi-zone illuminator 30).

Referring now to FIG. 5, one embodiment of a support structure isdepicted that enables adjustment of the distance between a substratework piece 20, energy transfer device 40, and support structure 48.Plural supports 50 can be affixed to or removable from a transparentsubstructure, such as quartz window 38. The distance between window 38and energy transfer device 40 can be adjusted by altering the length ofsupports 50. Similarly, the distance between energy transfer device 40and substrate 20 can be adjusted by altering the length of substrateheight adjustment pin 62. Alignment pins 51 maintain the position ofenergy transfer device 40 relative to window 38. Other pin arrangementsor supporting structure can be substituted as needed for substrates ofvarious sizes.

Referring now to FIG. 6, an alternative embodiment of energy transferdevice 40 is depicted. Energy transfer device 40 is comprised of asingle thin plate of material having physical properties that include ahigh emissivity approaching a value of one and a high thermalconductivity. For instance, the plate could be made of silicon carbideor materials coated with silicon carbide, such as aluminum nitride orgraphite. The plate can have a minimal thickness, such as betweenone-half and two millimeters. Plural slot or gaps 56 can be machined inthe plate as depicted to define high-emissivity, high-thermalconductivity regions D,R1, R2, and R3. Material left between the gapscan maintain the continuity of energy transfer device 40. Although FIG.6 depicts circular gaps and regions, alternative embodiments could usealternate geometric designs.

Referring now the FIG. 7, an alternative configuration of thermalprocessing system 10 is depicted in which substrate 20 is disposedbetween radiant energy source 30 and energy transfer device 40. Radiantenergy source 30 radiates energy directly to front side 22 of substrate20, and energy transfer device 40 radiates secondary energy at back side24 of substrate 20. In an alternative embodiment, thermal processingsystem 10 could be configured so that energy transfer device 30 couldirradiate back side 24 of substrate 20 while energy transfer device 40radiates secondary energy at frontside 22 of substrate 20. A pyrometryview port window 35 allows pyrometry sensor 34 to measure the energyfrom a region, such as region D, of energy transfer device 40 to allowadjustments of the energy irradiated from an associated zone of radiantenergy source 30. Thermocouples could also be used to measure the energylevel of the regions of energy transfer device 40 to support adjustmentsas described above. The configuration depicted by FIG. 7 advantageouslyallows indirect but accurate measurement of the energy level across thesubstrate by directly measuring the energy level at various regions ofenergy transfer device 40, with the energy level of the regions having adirect relationship to the energy level of associated areas of substrate20.

In summary, the high performance energy transfer device and relatedmulti-zone heating methodology described herein acts as an energy proxyby absorbing primary energy emitted by a heat source and then emittingsecondary energy to heat a substrate. The plural energy transfer regionsprovide accurate energy transfer from associated heating zones of theheat source without masking the effects of control inputs to the heatingzones, thus allowing independent control of different radial regions onthe work piece. The secondary energy emitted towards the substrate canbe accurately measured by sensors in physical contact with the emissiveregions, or can be measured using noncontact pyrometry sensors accordingto the predictable emissivity characteristics of each emissive region.

Although the present invention has been described in detail, it shouldbe understood that various changes, substitutions and alterations can bemade hereto without departing from the spirit and scope of the inventionas defined by the appended claims.

What is claimed is:
 1. A method for fabricating a device onto asubstrate, the method comprising the steps of: directing a radiativeenergy source at the substrate, the radiative energy source havingplural zones, each zone operable to provide a predetermined amount ofradiative energy; disposing plural energy transfer regions between theradiative energy source and the substrate, each energy transfer regionassociated with at least one zone; irradiating the plural energytransfer regions with radiative energy from the radiative energy source,the plural energy transfer regions absorbing the radiative energy toprovide secondary radiative energy to the substrate; measuring theenergy level of at least one energy transfer region; and adjusting theenergy level of the plural energy transfer regions by controlling theamount of radiative energy provided by the plural zones of the radiativeenergy source.
 2. The method according to claim 1 further comprising thestep of isolating each of the plural energy transfer regions bydisposing low-thermal-conductivity regions between the radiative energysource and the substrate so that heat transfer is suppressed between theadjacent energy transfer regions.
 3. The method according to claim 2wherein said adjusting step further comprises adjusting the energy levelof each energy transfer region to provide a substantially uniformfabrication process on the substrate.
 4. The method according to claim 2wherein said measuring step comprises measuring the energy levels of theplural energy transfer regions with plural temperature sensorsassociated with at least two of the plural energy transfer regions. 5.The method according to claim 2 wherein each of the plural energytransfer regions has an emissivity approaching a value of one.
 6. Themethod according to claim 2 wherein each of the plurallow-thermal-conductivity regions has low emissivity.
 7. The methodaccording to claim 2 wherein the irradiation step is performed inconjunction with rapid thermal processing to fabricate the device. 8.The method according to claim 2 further comprising the step of rotatingthe substrate relative to the plural energy transfer regions.
 9. Themethod according to claim 2 wherein each of the energy transfer regionshas a finite width, and wherein the energy transfer regions are disposeda predetermined distance from the substrate, the distance being smallerthan the widths of the energy transfer regions.
 10. The method accordingto claim 2 further comprising the step of minimizing the effects of theemissivity of the substrate with an optically reflecting surface facingthe substrate frontside.
 11. The method according to claim 9 wherein aquartz structure supports the energy transfer regions at thepredetermined distance.
 12. A method for fabricating a device onto asubstrate, the substrate having a front side and a back side, the methodcomprising the steps of: directing a radiative energy source at thefront side of the substrate, the radiative energy source having pluralzones, each zone operable to provide a predetermined amount of radiativeenergy; disposing plural energy transfer regions at the back side of thesubstrate, each energy transfer region associated with at least onezone; irradiating the plural energy transfer regions with radiativeenergy from the radiative energy source, the plural energy transferregions absorbing the radiative energy to provide secondary radiativeenergy to the substrate; measuring the energy level of at least oneenergy transfer region; and adjusting the energy level of the pluralenergy transfer regions by controlling the amount of radiative energyprovided by the plural zones of the radiative energy source.
 13. Themethod according to claim 12 further comprising the step of isolatingeach of the plural energy transfer regions by disposinglow-thermal-conductivity regions between the radiative energy source andthe substrate so that heat transfer is suppressed between the adjacentenergy transfer regions.
 14. The method according to claim 12 whereinsaid adjusting step further comprises adjusting the energy level of eachenergy transfer region to provide a substantially uniform fabricationprocess on the substrate.
 15. The method according to claim 12 whereinsaid measuring step comprises measuring the energy levels of the pluralenergy transfer regions with plural temperature sensors associated withat least two of the plural energy transfer regions.
 16. A method forfabricating a device onto a substrate, the method comprising the stepsof: disposing plural energy transfer regions between a radiant energysource and the substrate; illuminating the plural energy transferregions with radiant energy from the radiant energy source, the pluralenergy transfer regions operable to transfer more than one energy levelin response to the radiant energy; and emitting the radiant energyabsorbed by the plural energy transfer regions to provide secondaryradiant energy to the substrate.
 17. The method according to claim 16,further comprising the steps of: measuring the energy level of at leastone of the plural energy transfer regions; and adjusting the energylevel of the plural energy transfer regions by controlling the amount ofradiant energy provided by the radiant energy source.
 18. The methodaccording to claim 17, wherein the step of measuring further comprisesmeasuring the energy levels of the plural energy transfer regions withplural temperature sensors associated with at least two of the pluralenergy transfer regions.
 19. The method according to claim 17, whereinthe step of adjusting further comprises adjusting the amount of radiantenergy provided by the radiant energy source to selectively heatpredetermined positions along the substrate.
 20. The method according toclaim 16, wherein the radiant energy source has plural energy zones, atleast one energy zone associated with each energy transfer region. 21.The method according to claim 16, further comprising the step ofisolating at least two of the plural energy transfer regions bydisposing low thermal conductivity regions between the at least twoenergy transfer regions so that heat transfer is suppressed between theenergy transfer regions.
 22. The method according to claim 21, whereineach of the plural energy transfer regions has an emissivity approachinga value of one.
 23. The method according to claim 21, wherein each ofthe plural low thermal conductivity regions comprises an insulatingmaterial.
 24. The method according to claim 16, further comprising thestep of rotating the substrate relative to the plural energy transferregions.
 25. The method according to claim 16, wherein each of theplural energy transfer regions has a finite width.
 26. The methodaccording to claim 25, wherein the step of disposing further comprisesdisposing the plural energy transfer regions a predetermined distancefrom the substrate, the distance being smaller than the widths of theplural energy transfer regions.
 27. The method according to claim 26,wherein the plural energy transfer regions are supported at thepredetermined distance by a quartz structure.
 28. The method accordingto claim 16, further comprising forming an optical cavity system bydisposing an optically reflective surface facing the substratefrontside, the optically reflective surface minimizing the effects ofthe emissivity of the substrate.